1. Field of the Invention
The present invention relates to anthracene derivatives, and light-emitting devices, electronic devices, and lighting devices in which the anthracene derivatives are used.
2. Description of the Related Art
A light-emitting element utilizing a light-emitting organic compound has a structure in which a layer containing the organic compound is interposed between a pair of electrodes. Such a light-emitting element is characterized in that a thin and lightweight light-emitting element can be fabricated, light is emitted by applying direct current, and response is faster compared to liquid crystal displays, and the like. Moreover, the light-emitting devices in which such light-emitting elements are arranged in matrix form, i.e., passive matrix type light-emitting devices and active matrix type light-emitting devices, are superior to conventional liquid crystal displays in terms of wide viewing angle and excellent visibility. From these reasons, the light-emitting elements are expected to be applied to next-generation flat panel displays. In some cases, these light-emitting elements are referred to as electroluminescent elements or EL elements.
In the light-emitting elements, electrons are injected from a cathode into a layer containing an organic compound interposed between a pair of electrodes, and at the same time, holes are injected from an anode into the layer containing the organic compound, whereby a light-emitting element is driven. The electrons injected from the cathode and the holes injected from the anode are recombined with each other in the layer containing the organic compound to form molecular excitons. The molecular excitons release energy in relaxing to a ground state. When the energy is released as visible light, light emission can be observed. Excited states of organic compounds include a singlet excited state and a triplet excited state, and light can be emitted from both of the excited states.
An emission wavelength of the light-emitting element is determined by the energy gap between the ground state and the excited state formed by the recombination, i.e., a band gap. Therefore, a structure of a molecule that serves for emitting light is selected or modified as appropriate, whereby desired emission color of light can be obtained. A full color light-emitting device can be manufactured by using the light-emitting elements capable of emitting light of red, blue, and green colors that are three primary colors of light.
In order to manufacture a high performance full-color light-emitting device, red, green, and blue emissive light-emitting elements having a long lifetime, high emission efficiency, and excellent color purity are required. As a result of recent development of materials, as for the red and green emissive light-emitting elements, excellent characteristics have been attainable. However, as for a blue emissive light-emitting element, sufficient characteristics have not been obtained. For example, in Nonpatent Document 1 (J. Shi et al., Applied Physics Letters, 2002, Vol. 80, No. 17, pp. 3201-3203), a blue emissive light-emitting element with relatively high reliability is reported. However, sufficient emission efficiency and color purity are not realized. [Non-Patent Document 1]